Production of epsilon-caprolactam



dfiwfim l Patented Sept. 19, 1961 1 2 3 000 s77 period of time toproduce the epsiloncaprolactam. The PRODUCTION OF EPSILON QAPROLACTAMreaction mixture upon cooling, is subjected to conven- FRQM 6 ACET0XYCAPROIC ACID AND 1 3 tional recovery procedures such as extraction withchloro- LACTONE ADDUCTS form followed by distillation to recover theepsilon-capro- Benjamin Phillips, Charleston, Samuel W. Tinsley, South 5lactam thus produced.

Charleswn, and Paul siafchef, f i Y w The starting material,6-acetoxycaproic acid and its i g E sal'bide (1011361311011: 3corporatlon lactone adducts, is represented by the following formula: 0ew or No Drawing. Filed June 8, 1959, Ser. No. 818,504

4 Claims. (Cl. zeta-239.3) 10 GHs-O-O[(CHZ)U-CO]H This invention relatesto a process for the production of epsilon-caprolactam. Moreparticularly, this invention is directed to a non-catalytic process forthe production of epsilou-caprolactam by the reaction ofo-acetoxycaproic acid and its lactone adducts with aqueous ammonia underwherein x represents 1 through 5 units. The starting materials used toform the epsilon-caprolactam can exist in the following forms andcombinations thereof as follows:

superatmospheric pressures and in the temperature range OHtt3O(CHz)atiOH of 300 C. to 475 C. More specifically it is an object ofthis invention to provide a one-step process for the production ofepsilon-caprolactam. A particular object CH3OO-'(CH)5CO(OHz)iOOH of thisinvention is to provide a process for the produc- O 0 O 0 tion ofepsilon-caprolactam to the substantial exclusion v H H H I ofpolymerized material and in high yield efficiencies fromsz)sC0(CHs)5-CO(CH2)iCOH the 6-acetoxycaproic acid and its lactoneadducts to epsi- 0 O O O O lon-caprolactam. A further ob ect of th1slnvention 1s \1 H H H H to provide a continuous process for theproduction of w asepsilon-caprolactam. These and other objects will be-The saponification equivalents of the above compounds come readilyapparent to those skilled in the art in light can range from 87 to 106,Where the saponification equivof the teachings herein set forth. alentis the weight of product, in grams, which will react Lactams are usedfor the production of polyamides with one gram-mole of base understandard saponification suitable for the manufacture of fabrics, film,fibers, coatconditions. ing compositions and the like. Heretofore, theusual Concentrations of ammonium hydroxide for purposes preparation oflactams has been by Beckmann rearrangeof this invention can range from 2to 80 percent although ment of ketoximes. Caprolactam, the mostimportant these concentrations are not critical. Molar ratios of memberof this class, has long been prepared by reammonia to 6-acetoxycaproicacid and its lactone adducts araugement of cyclohexanone oxime. However,it has can vary from about 1:1 to about 2021 and more prefbeen necessaryto prepare cyclohexanone oxime intermeerably from about 3:1 to about10:1. While ratios above diate by means of one o more reacti ns, Fo examle, and below these amounts can also be employed they are thepreparation of the oxime by treating nitrocyclohexane a less preferredembodiment of this novel process. The or its salt with hydroxylamine,hydrogen, sulfur, sodium water diluent aids in the reaction to form themonomeric nitrite, and the like is well known in the art. It is alsopsilon-caprolactam. known to prepare cyclohexanone oxime b treatm nt ofThe 6-acetoxycaproic acid and lactone adducts can becyclohexanone-bisulfite complexes with nitrous acid and dissolved ininert Organic solvents such as toluene, like processes. Although suchmultistep processes for the Zens, ethylbefllene, oftho'Xylene, P ymeta'xylene preparation of lactams have generally produced satisfaeandthe like to facilitate adding the starting materials to tory products,the most desirable process is one whereby the reactants Of ammonia inwater. The presence of the lactarns eould be prepared i a single a dinexpensive organic solvents in the reaction of epsilon-caprolactonereaction. This invention provides a new and inexpensive, With ammoniadid not significantly afiect the reaction, non-catalytic method ofproducing epsilon-caprolactams The Process of this invention can e Caied Out 6011- by using inexpensive raw material with th e f tdtinuously, the residence time in the reaction zone being ard equipment.such that, in view of the high temperature and superat- The presentinvention is based on the discovery that mosphefic Pressures, maximumcollvefsiOHS Will be epsilon-caprolactam can be produced by reacting6-acetmilledoxycaproic acid and its lactone adducts with aqueous Thetime of reaction is not necessarily critical and y ammonia undersuperatmospheric pressures and high tem- Vary from 10 minutes to as muchas a y depending peratures. The maximum yield of monomeric epsilonon thereaction conditionscaprolactam in i invention approximates 50 percentThe term superatmospheric pressures, as used herein, per pass since theprocess involves a complex mixture of 1s i f as the pressures Producedby reactants on equilibria. However, recycling the reaction productsafter heatmg clostd vessel pressuuis as t as 680 removal of the formedmonomeric epsilomcapmlactam mospheres, if desired. Thls pressure 1smaintained for the duration of the reaction.

The epsilon-caprolactam may be isolated from the reaction mixture byextraction with chloroform or some other water-insoluble solvent andfurther purified by frac- Of Polymer1c P s tional distillation. Theunused 6-acetoxycaproic acid, its

The Process of thls lnvenllon 1s feadlly accompllshed lactone adductsand equilibrium products may then be reby heating 6-acetoxycaproic acidand its lactone adducts cycled fo f rther reaction, in a pressure vesselwith ammonium hydroxide over a The following examples illustrate anddescribe the temperature range of about 300 C. to 475 C., prefprocessinvolving the production of epsilon-caprolactam erably in the range of350 C. to 425 (3., for a suflicient in accordance with the invention.

under the conditions identical to those of the initial reactions,produces yield efiiciencies of epsilon-caprolactam as high as to percentto the substantial exclusion 3 EXAMPLE I A mixture of 60 grams (0.345mole) of 6-acetoxycaproic acid and 268 grams (4.4 moles) of 28 percentaqueous ammonia was heated to 350 C. for a period of 2.5 hours in astainless steel bomb. The reaction mixture was extracted with chloroformand chloroform layer was evaporated to dryness, leaving an 11 gramresidue (28 percent yield). The residue was. extracted With petro-' leumether. The petroleum ether extracts, upon cooling, gave 1 gram ofepsilon-caprolactam, melting point 64- EXAMPLE II Preparation ofepsilon-caprolactam from the lactone adducts of 6-acetoxycaproic acid Anester acid (145 grams) characterized by the formula:

What is claimed is:

1. A process for the production of epsilon-caprolactam which comprisesreacting a member of a group consisting of G-acetoxycaproic acid, and6-acetoxycaproic acid lactone adducts, said members characterized by theformula:

wherein at represents 1 through 5 units, with aqueous ammonia underpressures in the range consisting of autogenous pressure to 680atmospheres and in the temperature range from about 300 C. to about 475C. for a sufficient period of time to produce epsilon-caprolactam.

2. The process of claim 1 wherein the temperature ranges from about 350C. to about 425 C.

3. The process of claim 1 wherein the 6-acetoxycaproic acid lactoneadduct has a saponification equivalent in the range of 87 to 106.

4. A process for the production of epsilon-caprolactam which comprisesreacting 6-acetoxycaproic acid with aqueous ammonia under pressures inthe range consisting of autogenous pressure to 680 atmospheres and inthe tem perature range from about 300 C. to about 475 C. for asufficient period of time to produce epsilon-caprolactam.

References Cited in the file of this patent FOREIGN PATENTS 562,684Canada Sept. 2, 1958

1. A PROCESS FOR THE PRODUCTION OF EPSILON-CAPROLACTAM WHICH COMPRISESREACTING A MEMBERS OF A GROUP CONSISTING OF 6-ACETOXYCAPROIC ACID, AND6-ACETOXYCAPROIC ACID LACTONE ADDUCTS, SAID MEMBERS CHARACTERIZED BY THEFORMULA: